The invention relates to an inertial locking connector. More specifically, the invention relates to an inertial locking connector wherein an angle of inclination of mating corresponds to the number of poles in the connector to prevent incomplete mating.
An example of a conventional inertial locking connector is shown in FIG. 6 and disclosed in Japanese Utility Model Application Kokoku No. S58-41745. The connector shown in FIG. 6 has a male housing 100 and a female housing 200 that face each other and are formed to be mated with each other. The male housing 100 and the female housing 200 accommodate electrical contacts (not shown).
The male housing 100 has locking arms 102 that extend rearward from a base part 101. The base part 101 has an inclined surface at a front end (the right end in FIG. 6) of an upper surface of the male housing 100 (with respect to a direction of mating). Operating parts 103 project from upper surfaces of the locking arms 102 proximate rear end portions (with respect to the direction of mating) corresponding to free end portions of the locking arms 102. Locking projections 104 project from substantially central portions (with respect to the direction of mating) of the upper surfaces of the locking arms 102. The locking projections 104 have inclined surfaces 104a that have a steep gradient on a front surface (with respect to the direction of mating) and inclined surfaces 104b that have a shallow gradient on a rear surface (with respect to the direction of mating). The inclined surfaces 104a, 104b converge to form a point 104c. 
A male housing accommodating recess 203 is formed on a front part (the left end in FIG. 6) of the female housing 200 (with respect to the direction of mating). Locking parts 202 are formed on the front part (with respect to the direction of mating) of an upper wall 201 of the male housing accommodating recess 203. The locking parts 202 are formed to face an inside of the male housing accommodating recess 203. Inclined guiding surfaces 202a are formed on the front parts (with respect to the direction of mating) of the locking parts 202 for guiding the locking projections 104. Abutting step parts, which have a steeper inclination than the inclined guiding surfaces 202a, are formed on rear end portions of the locking parts 202 below the inclined guiding surfaces 202a. When the male housing 100 and female housing 200 are mated, the locking projections 104 bend the locking arms 102 downward while riding over the locking parts 202 and engage with the locking parts 202.
Another example of a conventional inertial locking connector is shown in FIG. 7 and disclosed in Japanese Japanese Utility Model Registration No. 2522319. The connector shown in FIG. 7 has a male housing 301 and a female housing (only a mating hood 401 of the female housing is shown) that face each other and are formed to be mated with each other. The male housing 301 and the female housing accommodate electrical contacts (not shown).
Locking arms 302 are arranged on an upper surface of the male housing 301 so that the locking arms 302 extend rearward from a front end (left end in FIG. 7(A)) with respect to a direction of mating. Operating parts 303 project from rear end portions (with respect to the direction of mating) of upper surfaces of the locking arms 302 corresponding to free end portions of the locking arms 302. Locking projections 304 project from substantially central portions (with respect to the direction of mating) of the upper surfaces of the locking arms 302.
Locking parts 402 project downward and are arranged on a front end (right end in FIG. 7(A)) of the mating hood 401 of the female housing with respect to the direction of mating. When the male housing 301 and the female housing are mated, the locking projections 304 bend the locking arms 302 downward while riding over the locking parts 402. The upper surfaces of the locking projections 304 are constructed as overriding sliding contact surfaces 304b. The overriding sliding contact surfaces 304b are inclined with respect to the direction of mating in a free state of the locking arms 302. The angle of inclination of the overriding sliding contact surfaces 304b substantially coincides with the maximum flexing angle of the locking arms 302. Contact surfaces 304a are formed on the front ends of the overriding sliding contact surfaces 304b with respect to the direction of mating. The contact surfaces 304a are inclined with respect to the direction of mating in the free state of the locking arms 302. The angle of inclination of the sliding contact surfaces 304a is greater than the angle of inclination of the overriding sliding contact surfaces 304b. 
When the male housing 301 and the female housing are mated, the contact surfaces 304a first contact the lower end edges of the front surfaces of the locking parts 402. As the male housing 301 advances in the direction of mating, the front end edges of the overriding sliding contact surfaces 304b ride over the lower end edges of the front surfaces of the locking parts 402, as shown in FIG. 7(A), so that the locking arms 302 reach a maximum flexing angle. In this state, the overriding sliding contact surfaces 304b are in a substantially horizontal position along the direction of mating. As the male housing 301 is inserted further into the female housing, the overriding sliding contact surfaces 304b slide along the bottom surfaces of the locking parts 402. The maximum flexing angle of the locking arms 302 is maintained until the rear end edges of the overriding sliding contact surfaces 304b reach the lower end edges of the rear surfaces of the locking parts 402. As the male housing 301 is inserted still further, the rear end edges of the overriding sliding contact surfaces 304b advance beyond the locking parts 402 and the locking arms 302 return to their original state to lock the locking projections 304 on the locking parts 402.
The relationship between the insertion stroke and the housing insertion force in the above-described series of mating operations is shown in FIG. 7(B). Specifically, the housing insertion force reaches its peak value (a) when the front end edges of the overriding sliding contact surfaces 304b ride over the lower end edges of the front surfaces of the locking parts 402 so that the locking arms 302 reach the maximum flexing angle shown in FIG. 7(A). The peak value (a) is determined by the angle of inclination of the contact surfaces 304a. The angle of inclination is the angle formed by a direction perpendicular to the direction of mating and the contact surfaces 304a. In instances where the angle of inclination is small, the peak value (a) of the housing insertion force is large. In cases where the angle of inclination is large, the peak value (a) of the housing insertion force is small.
When the overriding sliding contact surfaces 304b begin to slide along the bottom surfaces of the locking parts 402, the housing insertion force drops as indicated at (b) in FIG. 7(B). This housing insertion force is maintained until the rear end edges of the overriding sliding contact surfaces 304b reach the lower end edges of the rear surfaces of the locking parts 402. When the rear end edges of the overriding sliding contact surfaces 304b leave the locking parts 402, the housing insertion force becomes zero in a single stroke as indicated at (c) in FIG. 7(B), and the locking projections 304 are instantly locked on the locking parts 402.
Since the housing insertion force has an initial maximum peak value (a) that then decreases until the locked state (c) is reached, this type of connector is called an inertial locking type connector. Specifically, during mating of the connectors, an worker must initially apply some degree of housing insertion force. The insertion force, however, subsequently rapidly decreases so that the connector is inertially pushed into a locked state in a single stroke. As a result, a state of incomplete mating can be prevented.
In the inertial locking type connector, the peak value (a) of the housing insertion must be slightly greater than the overall load arising from mating the plurality of electrical contacts that contact each other in order to prevent incomplete mating. If the peak value (a) is not slightly greater than the overall load, the worker can not inertially mate the connector. Because the worker generally looks at the size or number of poles of the connector and roughly estimates the force required for mating, if the angle of inclination is uniformly set at a small value regardless of the number of poles, the peak value of the housing insertion force will exceed the overall load when the number of poles is small. Thus, a housing insertion force exceeding the estimate made by the worker is required to inertially mate the connectors and as such unfavourable mating of the connectors occurs.
It is therefore desirable to develop an inertial locking connector wherein the angle of inclination of the contact surfaces of the locking projections can be varied in accordance with the number of poles so that a state of incomplete mating can be prevented and the characteristics of the mating operation of connectors with a small number of poles can be improved.
The invention relates to an inertial locking connector. The inertial locking connector has a male housing having a locking arm with a locking projection. The locking projection has a contact surface formed on a front end of the locking projection with respect to a direction of mating and at an inclination with respect to the direction of mating. The contact surface engages a locking part on a female housing when the male housing and the female housing are mated. The male housing has an angle of inclination formed by a direction perpendicular to the mating direction and the contact surface. The angle of inclination decreases as the number of poles of electrical contacts increases in the female housing.